File Specificatons

OCA Data

The OCA data is stored in a standard text file.

• The file extension must be .oca.
• The text encoding must be UTF-8.
• The data must be formatted as JSON.
  We chose JSON (over XML or YAML ) because it is both very easy to use with any programming language, and easy to read and edit by humans.
  • The JSON string should be pretty printed, with a 4-space indentation.
    This makes it easier to read by humans.
  • There must be a single Root Object which itself contains all data.
  • There must not be any other data than what is listed in this document.
    This is needed to prevent potential conflicts with future updates.

Document Metadata

Any metadata associated to the whole document must be stored in the metadata file.

The metadata is separated from the main OCA data file to make it easy for users to strip (or replace) all metadata from the file.

• It must have the same name as the OCA Data file, suffixed with _meta, and the file extension must be .json.
• The text encoding must be UTF-8.
• The data must be formatted as JSON.
  • The JSON string should be pretty printed, with a 4-space indentation.
  • There must be a single Metadata Object which itself contains all metadata.

Image Data

Image data is stored in standard image files, according to the type sepcified in the OCA data file.

• For paintlayers and U8 or U16 color depths, images must be PNG files.
  • Their colorspace must be sRGB.
  • Their color depth must correspond to the color depth set in the OCA data
    (U8 for 8-bit integer, U16 for 16-bit integer).
  • There can be only a single color depth used for the whole document.
  • The alpha channel must not be premultiplied.
• For paintlayers and F16 or F32 color depths, images must be openEXR files.
  • Their colorspace should be linear RGB.
    There’s no way yet to specify the color space with OCA; you may add its name in the file name.
  • Their color depth must correspond to the color depth set in the OCA data
    (F16 for “half” 16-bit float, F32 for 32-bit float).
  • There can be only a single color depth used for the whole document.
  • They should not use the Luma/Chroma option.
  • They must contain at least four channels called R, G, B, A, and the may contain other AOVs.
  • The alpha channel must be premultiplied with black.
• For vectorlayers, images must be SVG files.